1. Field of the Art
The present invention relates to a dye intermediate, a dye and a thermal transfer sheet. More particularly, it is concerned with an intermediate capable of providing a dye excellent in the coloring density, sharpness, light fastness, safety, etc., a dye and a thermal transfer sheet excellent in the above-described properties.
2. Background Art
Various thermal transfer processes are known in the art. Among them, a sublimation transfer process has been practiced which comprises supporting a sublimable dye as a recording agent on a substrate sheet, such as paper, to form a thermal transfer sheet, putting the thermal transfer sheet on a transfer material dyeable with a sublimable dye, for example, a polyester woven fabric, and applying a thermal energy in a pattern form from the back surface of the thermal transfer sheet to transfer the sublimable dye to the transfer material.
In recent years, a proposal has been made on a process wherein various full color images are formed on paper or a plastic film through the use of the above-described sublimation type or thermal transfer system. In this case, a thermal head of a printer is used as heating means, and a number of color dots of three or four colors are transferred to the transfer material, thereby reproducing a full color image of an original by means of the multicolor dots.
Since the color material used is a dye, the image thus formed is very clear and highly transparent, so that the resultant image is excellent in the reproducibility and gradation and the quality of the image is the same as that of an image formed by the conventional offset printing and gravure printing. In this method, it is possible to form an image having a high quality comparable to a full color photographic image.
The most important problem in the thermal transfer process resides in the color density, sharpness and light fastness of the formed image, and no dye which could have sufficiently solved these problems are known in the art.